Traditionally, a wet conductive adhesive paste has been used to adhere a semiconductor die or chip to a substrate in die bonding. An external heating and pressurizing means, which is referred to as a thermocompression means, is used to cure and press the adhesive paste underneath the die against the substrate so as to bond the die and the substrate together. In recent years, the continual reduction in thickness of dies from 500 to 25 μm has made a great impact on semiconductor die packages and their resulting electronic products as these thin dies not only enable ultrathin applications (e.g., smart cards, biological passports, etc.) but also promote ultrahigh-density applications (e.g., memories, CPUs, etc.). Problems of using a traditional adhesive paste in bonding a die of such thinness have been adhesive overflow and adhesive spread-out which cause an unavoidable short-circuit failure.
Dry conductive adhesive films or tapes such as Die Attach Film (DAF) or Thermoplastic Adhesive Tape (TAT) were developed to replace the traditional wet conductive adhesive pastes, especially in bonding thin dies of thicknesses less than 75 μm. DAF is usually laminated on the backside of the wafer before dicing the wafer into individual dies, while TAT is usually attached to the backside of individual dies after the wafer dicing process. A die laminated with DAF or TAT can be directly bonded to a substrate using heat and pressure which is referred to as thermocompression bonding and is also regarded as the state-of-the-art bonding method. Problems with this method have been a high bonding temperature of 100 to 180° C., a long bonding time of at least 3 seconds, a single die bonding per bonding cycle and a continual heating of fresh and post-bonded dies, adhesives and substrates throughout the bonding process. Yet void formation along the die-adhesive-substrate interfaces, a constrained bonding process window, a low throughput and the inability to use less expensive substrates such as synthetic resin bonded papers (SRBP, FR-1 and FR-2) which have lower operational temperatures than the bonding temperature of DAF or TAT have often occurred. The high temperature and lengthy heat exposure affects the reliability of the die package and bonding equipment.
There is a desire for a bonding method and system to address at least some of the abovementioned problems.